The discovery may mean we will soon have a new way of fighting viral infections, from stomach bugs to seasonal colds and flu.

The bark of the willow tree is thought to have been used for centuries as a traditional medicine to relieve pain. Its active ingredient, salicin, was discovered in 1828 and used to create salicylic acid 10 years later. Then, in 1899, scientists at the drug firm Bayer modified salicylic acid to create acetylsalicylic acid, otherwise known as aspirin.

Now, a Finnish study led by researchers at the University of Jyväskylä has found that willow bark extract might also be an effective, broad-spectrum antiviral agent.

"We need broadly acting and efficient tools to combat the virus load in our everyday life," said Varpu Marjomäki, corresponding author of the study. "Vaccinations are important, but they cannot deal with many of the newly emerging serotypes early enough to be effective on their own."

In a previous study, the researchers had tested willow bark (Salix) extract on non-enteroviruses, a group of RNA viruses such as those that cause polio and hepatitis A, and found it to be very effective and non-toxic. In the current study, they tested the extract on other kinds of viruses to see if it was effective and to try and understand its mechanism of action.

The extract was made by harvesting bark from commercially grown willow branches, which the researchers cut up, froze, ground, and extracted using hot water. The researchers then tested it on cell samples with two strains of enteroviruses, Coxsackievirus A (CVA) and B (CVB), and two coronaviruses, a seasonal coronavirus and SARS-CoV-2, which causes COVID-19.